The present invention relates generally to the field of underground boring and, more particularly, to a closed-loop control system and process for controlling the operations of an underground boring machine in real-time.
Utility lines for water, electricity, gas, telephone and cable television are often run underground for reasons of safety and aesthetics. In many situations, the underground utilities can be buried in a trench which is then back-filled. Although useful in areas of new construction, the burial of utilities in a trench has certain disadvantages. In areas supporting existing construction, a trench can cause serious disturbance to structures or roadways. Further, there is a high probability that digging a trench may damage previously buried utilities, and that structures or roadways disturbed by digging the trench are rarely restored to their original condition. Also, an open trench poses a danger of injury to workers and passersby.
The general technique of boring a horizontal underground hole has recently been developed in order to overcome the disadvantages described above, as well as others un addressed when employing conventional trenching techniques. In accordance with such a general horizontal boring technique, also known as microtunnelling, horizonal directional drilling (IIDD) or trenchless underground boring, a boring system is situated on the ground surface and drills a hole into the ground at an oblique angle with respect to the ground surface. A drilling fluid is typically flowed through the drill string, over the boring tool, and back up the borehole in order to remove cuttings and dirt. After the boring tool reaches a desired depth, the tool is then directed along a substantially horizontal path to create a horizontal borehole. After the desired length of borehole has been obtained, the tool is then directed upwards to break through to the surface. A reamer is then attached to the drill string which is pulled back through the borehole, thus reaming out the borehole to a larger diameter. It is common to attach a utility line or other conduit to the reaming tool so that it is dragged through the borehole along with the reamer.
In order to provide for the location of a boring tool while underground, a conventional approach involves the incorporation of an active sonde disposed within the boring tool, typically in the form of a magnetic field generating apparatus that generates a magnetic field. A receiver is typically placed above the ground surface to detect the presence of the magnetic field emanating from the boring tool. The receiver is typically incorporated into a hand-held scanning apparatus, not unlike a metal detector, which is often referred to as a locator. The boring tool is typically advance by a single drill rod length after which boring activity is temporarily halted. An operator then scans an area above the boring tool with the locator in an attempt to detect the magnetic field produced by the active sonde situated within the boring tool. The boring operation remains halted for a period of time during which the boring tool data is obtained and evaluated. The operator carrying the locator typically provides the operator of the boring machine with verbal instructions in order to maintain the boring tool on the intended course.
It can be appreciated that present methods of detecting and controlling boring tool movement along a desired underground path is cumbersome, fraught with inaccuracies, and require repeated halting of boring operations. Moreover, the inherent delay resulting from verbal communication of course change instructions between the operator of the locator and the boring machine operator may compromise tunneling accuracies and safety of the tunneling effort. By way of example, it is often difficult to detect the presence of buried objects and utilities before and during tunneling operations. In general, conventional boring systems are unable to quickly respond to needed boring tool direction changes and productivity adjustments, which are often needed when a buried obstruction is detected or changing soil conditions are encountered.
During conventional horizontal and vertical drilling system operations, the skilled operator is relied upon to interpret data gathered by various down-hole information sensors, modify appropriate controls in view of acquired down-hole data, and cooperate with other operators typically using verbal communication in order to accomplish a given drilling task both safely and productively. In this regard, such conventional drilling systems employ an xe2x80x9copen-loopxe2x80x9d control scheme by which the communication of information concerning the status of the drill head and the conversion of such drill head status information to drilling machine control signals for effecting desired changes in drilling activities requires the presence and intervention of an operator at several points within the control loop. Such dependency on human intervention within the control loop of a drilling system generally decreases overall excavation productivity, increases the delay time to effect necessary changes in drilling system activity in response to acquired drilling machine and drill head sensor information, and increases the risk of injury to operators and the likelihood of operator error.
There exists a need in the excavation industry for an apparatus and methodology for controlling an underground boring tool and boring machine with greater responsiveness and accuracy than is currently attainable given the present state of the technology. There exists a further need for such an apparatus and methodology that may be employed in vertical and horizontal drilling applications. The present invention fulfills these and other needs.
The present invention is directed to systems and methods for controlling an underground boring tool. A control system of an underground boring machine receives data from sensors provided at the boring machine, at the boring tool, and optionally at an aboveground site separate from the boring machine location. Various sensors monitor boring machine activities, boring tool location, orientation, and environmental condition, geophysical and/or geologic condition of the soil/rock at the excavation site, and other boring control system activities. Data acquired by these sensors is processed by a boring machine controller to provide closed-loop, real-time control of a boring operation.
In general terms, the boring system comprises an apparatus for driving a boring tool along an underground path in a desired direction. The driving apparatus may, for example, to comprise a rotation unit which includes a rotation unit sensor that senses a parameter of rotation unit performance. The rotation unit further includes a rotation unit control that moderates rotation unit performance. The driving apparatus may also comprise a displacement unit which includes a displacement unit sensor that senses a parameter of displacement unit performance. The displacement unit further includes a displacement unit control that moderates displacement unit performance. A boring tool is coupled to a drill pipe, also termed a drill string or drill stem. The drill is coupled to the rotation unit for rotating the boring tool and to the displacement unit for displacing the boring tool along an underground path.
An exemplary system and method for controlling an underground boring tool according to the principles of the present invention involves rotating the boring tool and sensing a parameter of boring tool rotation. The boring tool is also displaced in a forward or reverse direction relative to the boring machine and a parameter of boring tool displacement is sensed. A controller produces a control signal substantially in real-time in response to the detected boring tool location and the sensed boring tool rotation and displacement parameters. The control signal is applied to one or both of the boring tool rotation and displacement pumps or motors so as to control one or both of a rate and a direction of boring tool movement along the underground path. Detecting the location of the boring tool and computing the control signal preferably occurs within about 1 second or less.
A closed-loop control system, according to an embodiment of the present invention, comprises a controller which is communicatively coupled to a rotation unit sensor and control, and a displacement unit sensor and control of the boring tool driving apparatus. The controller is also communicatively coupled to the sensors and electronic components of the boring tool. The controller receives telemetry data from the sensors of the down-hole sensor unit substantially in real-time and transmits control signals to each of the rotation and displacement unit controls substantially in real-time so as to control one or both of a rate and a direction of boring tool movement along the underground path in response to the received telemetry data. A response time associated with acquiring boring tool location data and the controller receiving the boring is tool location data is about 1 second or less. Further, a response time associated with acquiring boring tool location data, the controller receiving this data, and the controller transmitting control signals to each of the rotation and displacement unit controls is about 1 second or less.
In one embodiment, the down-hole sensor unit includes one or both of an accelerometer and/or a magnetometer. Telemetry :data is communicated electromagnetically, optically or via a mud pulse technique between the down-hole sensor unit and the controller. Telemetry data may be communicated between the down-hole sensor unit and the controller via a communication link established via the drill string or via an above-ground tracker unit. The communication link established via the drill string may comprise an electrical or optical fiber passing through the drill string, or an electrical conductor integral with each connected segment of the drill string. The tracker unit may be of a conventional design, and may be functionally equivalent to a conventional locator. Alternatively, the tracker unit may have a more advanced design, and provide for enhanced functionality, as will later be described hereinbelow. In one embodiment, the tracker unit comprises a hand-held or portable transceiver.
The controller determines a location of the boring tool with reference to a known initial location, such as a known entry point at which the boring tool initially penetrates the earth""s surface. The entry location is preferably defined in teres of x-, y-, and z-plane coordinates, or, alternatively, in terms of latitude, longitude, and elevation. The controller determines the location of the boring tool using the boring tool telemetry data received from the down-hole sensor unit and/or the tracker unit. In accordance with one embodiment, the controller determines the boring tool location using a successive approximation approach, by which the change of boring tool position is based on the displacement of the drill string and the telemetry data received from the down-hole sensor unit and/or tracker unit. The location of the boring tool may be expressed in terms of position (e.g., x-, y-, z- plane coordinates) and/or orientation (e.g., pitch (up/down) and yaw (left/right)).
The tracker unit may receive an electromagnetic or acoustic signal from the boring tool. In one embodiment, the tracker unit comprises a ground penetrating radar (GPR) unit. According to this embodiment, the boring tool includes a receiver and a signal processing device. The boring tool receiver receives a probe signal transmitted by the GPR unit, and the signal processing device generates a boring tool signal in response to the probe signal. The boring signal according to this embodiment has a characteristic that differs from the probe signal in one of timing, frequency content, information content, or polarization.
In accordance with another embodiment, the tracker unit includes a number of spaced apart apart antenna cells situated along the underground path. A least one of the antenna cells receives the boring tool signal and communicates the received boring tool signal to other antenna cells for reception by the controller. In another embodiment, the tracker unit comprises a hand-held or portable transceiver which detects the boring tool signal and transmits the detected signal to the controller.
The boring system may further include an interface that couples the controller with the down-hole sensor unit. The interface is configurable, either manually or automatically, in order to accommodate each of a number of different down-hole sensor units each having differing characteristic interface requirements.
The rotation unit may include a rotation pump or a rotation motor, and the displacement unit may include a displacement pump or a displacement motor. The rotation unit may constitute one of a mechanical, hydrostatic, hydraulic or electric rotation unit, and the displacement unit may constitute one of a mechanical, hydrostatic, hydraulic or electric displacement unit. The rotation unit and displacement unit sensors may each comprise a pressure sensor and/or a velocity sensor.
The boring system may further include a rotation unit vibration sensor and a displacement unit vibration sensor. One or more vibration sensors may also be mounted to the boring system chassis or other structure for purposes of detecting displacement or rotation of the boring system chassis or high levels of chassis vibration during a boring operation. The controller receives signals from the rotation and displacement unit vibration sensors and the chassis vibration sensors substantially in real-time and further modifies one or both of the rate and the direction of boring tool movement along the underground path in response to the signals received from the vibration sensors.
The boring tool may further include a steering mechanism for directing the boring tool in a desired direction. The controller controls the steering mechanism to modify one or both of the rate and the direction of boring tool movement along the underground path. The steering mechanism may include one or more of an adjustable plate-like member, an adjustable cutting bit, an adjustable cutting surface or a movable mass internal to the boring tool. The steering mechanism may also include one or more adjustable fluid jets. The boring tool may further include one or more cutting bits each of which includes a wear sensor for indicating a wear condition of the cutting bit.
One or more geophysical sensors may be deployed within the boring tool or external of the boring tool for sensing one or more geophysical characteristics of soil/rock along the underground path. The controller may further modify one or both of the rate and the direction of boring tool movement along the underground path in response to signals received from the geophysical sensors. A radar unit and/or other geophysical sensors may be employed within or proximate the boring tool or, alternatively, within an aboveground system for detecting man-made and geophysical structures and characterizing the geology at the excavation site. The boring system may also include a display for displaying a graphical representation of one or more of a boring tool location, orientation, the underground path, underground structures or boring tool movement along the underground path. Underground hazards and utilities, for example, may be graphically depicted in the display. Such a display may be provided on the boring machine, on a portable tracker unit, or both.
The delivery of fluid, such as a mud and water mixture, to the boring tool may be controlled during excavation. Various fluid delivery parameters, such as fluid volume delivered to the boring tool and fluid pressure and temperature, may be controlled. The viscosity of the fluid delivered to the boring tool, as well as the composition of the fluid, may be selected, monitored, and adjusted during boring activities. Adjustments may be made as a function geophysical information, rock or soil type, rotation torque, pullback or thrust force, etc.
A portable remote unit may be used by an operator to control boring machine activities from a site remote from the boring machine. The remote unit may issue boring and steering commands directly to the boring machine or to down-hole electronics provided at the boring tool. Control signals that effect boring machine operational changes may be produced by the remote unit, the down-hole electronics, the controller of the boring machine, or through cooperation of two or more of the remote unit, down-hole electronics, and boring machine controller.
The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. Advantages and attainments, together with a more complete understanding of the invention, will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.